High-power Chemical Oxygen-iodine Laser Research Articles

Three dimensional transient analysis of bubble dynamics in centrifugal bubble singlet oxygen generator for scalable COIL

Chemical Oxygen Iodine Laser (COIL) is the shortest wavelength (1.315 μm) chemical laser employing singlet oxygen molecules as the pumping species and iodine atoms as lasing species. Singlet Oxygen Generator (SOG) is essentially the heart of this laser device which is basically a gas–liquid phase chemical reactor. SOG facilitates the reaction between a basic hydrogen peroxide solution (BHP, H2O2 + KOH) and chlorine gas to produce singlet oxygen molecules. Centrifugal Bubble Single Oxygen Generator (CBSOG) is a potential candidate for an alternative SOG with better operating conditions for high throughput and high power COIL systems. In CBSOG Chlorine gas is bubbled through a layer of BHP solution and the required reaction takes place at the gas–liquid interface of the formed bubbles under high speed rotation of the chamber for gravity independent operation. The performance of this device largely depends on the bubble formation characteristics and their traverse inside the BHP layer. The aim of this paper is to present the numerical analysis of the mechanics of bubble formation, detachment and movement in the BHP layer for different operating parameters as applicable to COIL. The determination of conditions for the transition from bubbling to the jetting regime at different centrifugal accelerations of high magnitude (G ∼ 204 g, 306 g & 387 g) with low liquid column thickness (∼6–8 mm) operating under low pressure (∼100 torr) is another point of focus. The Volume of Fluid (VOF) method has been used for the 3-D transient interface tracking between the phases. This paper also compares the simulation results for various gas flow rates and centrifugal accelerations with select experimental results reported elsewhere showing reasonably good agreement.

Intracavity polarization control of high power chemical oxygen-iodine laser

The polarization of a high-power chemical oxygen-iodine laser (COIL) affects the beam quality, emission, and transmission of the COIL. We paper demonstrate an intracavity polarization control method for high-power COILs using a polarization beamsplitter mirror, which has the characteristics of high transmission of P light and high reflection of S light. To realize intracavity polarization control of a high-power COIL, we use the beamsplitter as a mirror in the COIL cavity. Finally, we attain the linear polarization laser output, and the linearity of the polarization approaches 1. At the same time, the power of the COIL is not significantly lost, and the mirror is able to withstand the high-power density without exhibiting thermal damage.

Unstable resonators of high-power chemical oxygen—iodine lasers

Configurations of unstable resonators are considered depending on the basic parameters of a high-power chemical oxygen—iodine laser and the design of an unstable resonator is proposed which provides the compensation of the inhomogeneity of the small-signal gain downstream of the active medium, a high energy efficiency, and stability to intracavity aberrations. The optical scheme of this resonator is presented and its properties are analysed by simulating numerically the kinetics of the active medium and resonator itself in the diffraction approximation.

Output beam drift and deformation in high-power COIL

During the operation of a chemical oxygen iodine laser (COIL) with an unstable resonator of a large Fresnel number, as the output power increases, an instability of the output laser beam will appear, behaving mainly as far-field beam spot drift and deformation. In order to interpret this phenomenon, thermal expansion analysis on the scraper with finite element analysis method and a simulation of the output beam mode of this kind of laser by the method of Fast Fourier Transform were developed. From the experimental measurement and the calculation, we proposed that the presence of the nonuniform temperature distribution of scraper causes the front surface of the scraper to tilt and bulge due to thermal expansion. As the output power is increasing, all the mirror surfaces, especially the scraper's, will absorb more and more heat, causing thermal expansion of the mirror front surface to occur more seriously, thus resulting in the tilting and deformation of the far-field beam spot. The initial misalignment of the direction is also an important factor leading to the far-field beam spot drift and deformation.

Study on Material Processing of Chemical Oxygen Iodine Laser.

This work describes a chemical oxygen iodine laser (COIL) equipment and its application for material processing of cutting and welding. The COIL is capable of delivering high-power output. The shortwavelength (1315 nm) is suitable for the transmission using optical fibers with excellent beam quality. These characteristics make COIL a candidate for a variety of industrial applications in cutting and welding. A cutting application in decommissioning of nuclear reactors is one purpose of high power COIL system and a welding application in heavy industries of thick material is another purpose. The most important key requirement for an industrial laser is low operating cost. At this point of view there are many kinds of problemsto be solved for industrial application of COIL.

Scaling laws for thick-section cutting with a chemical oxygen–iodine laser

Almost all laser-assisted materials processing involves melting, vaporization and plasma formation which affect the utilization of laser energy for materials processing. To account for the effect of these phases, an effective absorptivity is defined, and a simple mathematical model is developed for the cutting of thick-section stainless steel using a high power chemical oxygen—iodine laser (COIL). The model is based on an overall energy balance, and it relates the cutting depth with various process parameters that can be used to predictively scale the laser materials processing performance to very thick sections. The effects of various process parameters such as laser power, spot size, cutting speed and cutting gas velocity on the cutting depth are discussed. The results of the mathematical model are compared with experimental data. Such a comparison provides a means of determining the effective absorptivity during laser materials processing.

Heuristic method for evaluating COIL performance

A heuristic methodology is described that was developed to evaluate the chemical efficiency of high-power chemical oxygen iodine laser (COIL) devices and its application to the specific evaluation of the U.S. Air Force Phillips Laboratory's RotoCOIL laser. A heuristic equation that forms the basis of this methodology and describes the COIL energy flow, energy losses, and power extraction using measured data, code results, and empirical relations is presented. Using this equation and bounding values for some of its terms, it is shown that for the RotoCOIL performance data the experimentally measured average O 2 ( 1 Δ) yield of 0.40 is nearly 38% below that which would be consistent with the measured extraction power. By relating terms of the heuristic equation to performance of individual components of the COIL system, it is concluded that nearly 50% of the efficiency loss for the RotoCOIL laser derives from oxygen generator and delivery losses, whereas 15% is from nozzle inefficiencies and 11% from resonator losses.

Theoretical and experimental studies of thick-section cutting with a chemical oxygen–iodine laser (COIL)

A simple mathematical model of thick-section stainless steel cutting with a high power chemical oxygen–iodine laser (COIL) is presented and compared with experimental results obtained with a 10-kilowatt COIL at the U.S. Air Force's Phillips Laboratory. This model uses a lumped-parameter technique to relate the cutting kerf depth with various process parameters and can be used to predict scaled laser materials processing performance to very thick sections. The model is similar to an empirical model developed by researchers in Japan, but includes predictive capabilities for thick metal cutting at very low velocities. The effects of various process parameters such as laser power, spot size and dimensions, and processing speed in the cutting depth are discussed and demonstrated. Finally, the ramifications of this model on thick-section processing of metals are presented, with emphasis on potential applications of COIL to high-speed, thick stainless steel cutting.

Effect of the Gas Temperature of a High-Power Chemical Oxygen-Iodine Laser on Calculated Small Signal Gain and Output Power

Rate equations describing the lasing kinetics of a high-power chemical oxygen-iodine laser were solved, taking into account the effect of gas temperature. The temperature rise resulting from deactivations was calculated at each computation step along the flow, with the temperature dependence of rate constants and of the heat capacitance of the total gas taken into account. It has been shown that the inclusion of the temperature effect has a significant influence on the calculated laser gain and laser output. The results of the present calculation verify the observation of surprisingly high gas temperature in the optical resonator in a previous experiment and indicate that the gas temperature of a subsonic, 1 kW-class chemical oxygen-iodine laser can easily be over 1000° C in the optical resonator unless a buffer gas is used to increase the heat capacitance.

Experimental investigation of chemical oxygen-iodine laser

Results of an experimental investigation of a chemical oxygen-iodine laser (COIL) are presented. We determine the factors influencing the efficiency of a chemical singlet-oxygen generator (SOG) of the bubbler type operating on the chlorination of an alkaline solution of oxygen peroxide. We describe SOG constructions. A cw COIL with output power up to 400 W is developed on the basis of the investigated SOG. The feasibility of a modular construction of high-power COIL is demonstrated. A power-output level of 1 kW was achieved with a two-section laser. The feasibility is analyzed of COIL operation in a pulsed regime by pulsed bulk accrual of iodine atoms. We show that in this regime the laser can be operated without a low-temperature trap. An advantage of such a regime is also the possibility of controlling, in a wide range, the lasing pulse duration. A strong influence of molecular chlorine on the energy content of the active medium is observed when alkyliodides are used as iodine donors. The possibilities of using a pulsed COIL for controlled thermonuclear fusion are discussed.

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and our high-power chemical oxygen-iodine laser as an analysis model. By locating the telescope at a proper position on the optical axis, the overall telescopic resonator can be conveniently tailored to the hardware of this model laser in a way that the beam divergence and the resonator stability can be improved simultaneously. Experiments are carried out for one of the conditions used in the calculations. Measured divergence angles are in excellent agreement with the theoretical values.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>